1. Field of the Invention
The present invention relates to a system which efficiently pipes visible light into a greenhouse or other enclosure, but which excludes ultraviolet and infrared light.
2. Description of the Prior Art
U.S. Pat. No. 4,297,000 discloses a solar lighting system in which light energy from the sun is directed by a solar collection device onto the end of a bundle of optical fibers. However, the system shown therein does not contain any means for filtering out various light frequencies.
U.S. Pat. No. 4,539,625 discloses a combined lighting system for a building interior including a stack of luminous solar concentrators, an optical conduit made of preferably optical fibers for transmitting light from the concentrator stack, a lens set at an angle, and a fixture for receiving the daylight at one end and for distribution the daylight as illumination inside the building. However, this reference also fails to contains means for filtering out various light frequencies. Other references of some relevance to the present invention are briefly described below.
U.S. Pat. No. 4,626,065 discloses a light conduction apparatus for photosynthetic reaction including a rotatable light distributor which may be a transparent rod or a disk.
U.S. Pat. No. 4,600,973 discloses a device employing light energy transmitted through an optical conductor cable as a photo-sensitizing light source for cultivating plants.
U.S. Pat. No. 2,815,607 describes a process and apparatus for growing or culturing photosynthetic microorganisms or macroorganisms and includes a light conducting device.
European Patent No. 0189,177 describes a system wherein light from an external source is transmitted by optical cable to an optical-fluid-filled transparent cylinder and radiated outwards by a reflecting piston structure, moveable up and down the cylinder by displacement of fluid from one side of the piston to the other and is used in controlled iluminating for photosynthetic and indoor cultivation of plants.
U.S. Pat. No. 4,525,031 discloses a solar energy and electric lighting system. When solar energy is available as in daytime, it is utilized for lighting in lieu of conventional electric lamps, but when no solar energy is available or the solar energy available is not sufficient the electric lamps are turned on.
British specification No. 607,923 discloses a reflector for use with interior lighting appliances such as fluorescent tubes to concentrate the light emanating therefrom in a desired direction.
It is noted that none of the above references contain any means for filtering out the various light frequencies.
Other references of interest include the following:
British specification No. 1,138,162 discloses a light unit including a source of visible and infrared radiant energy in combination with a reflector capable of reflecting substantially all of the infrared radium energies and a predetermined portion of the visible radiant energies to obtain a color corrected light. The term "color correction" as used therein, means the modification of the spectral balance of a beam of light, after its emission by a source, to a desired color temperature.
The publication "The Ultraviolet Transmission of Various New Glasses And Window Glass Substitutes As Compared With That Of Common Window Glass" published by the Department of Commerce on Jan. 14, 1928 is of interest in showing the transmission properties with respect to ultraviolet light of various glasses as compared to common window glass.